Electrical apparatus



Nov. 17, 1959 M. w. BURGHER ELECTRICAL APPARATUS Filed NOV- 2. 1956INVENTOR.

MAURICE W. BURGHER ATTORNEYS United States Patent i ELECTRICAL APPARATUSMaurice W. Burgher, Sidney, N.Y., assignor to Bendix AviationCorporation, Sidney, N.Y., a corporation of Delaware ApplicationNovember 2, 1956, Serial No. 620,022

Claims. (Cl. 339-26) This invention relates to electrical apparatus andmore particularly to apparatus for connecting the terminal ends of twoelectrical conductors.

One of the objects of the present invention is to provide novelapparatus for effecting a raido-shielded connection of electricalconductors.

Another object of the invention is to provide an electrical terminalconnection wherein continuous insulation of the conductors is attainedin a novel manner.

A further object of the invention is to provide novel apapratus meansfor effectively preventing fiashovers be= tween highpotential conductorsand parts which are'at a lower or ground potential. a

A still further object of the invention is to provide novel sealingmeans to prevent moisture from intering the radio-shielded terminalconnection.

Still another object is to provide an electrical connection wherein afirm connecton of the insulation surround ing the conductors is effectedautomatically and'simultaneously with the connection of theradio-shielding means around the conductors.

The above and further objects and novel features of the invention willmore fully appear from the following detailed description when the sameis read in connection with the accompanying drawings.

' It is to be expressly understood, however, that the drawings are forthe purpose of illustration only andare not intended as a definition ofthe limits of the inven tion.

Referring now to the drawings wherein'like reference characters refer tolike parts throughout the several views:

Fig. 1 shows a side elevation, with parts broken away and partly insection of a shielded spark plug and terminal connection therefor;

Fig. 2 is an expanded view of a portion of Fig. '1 in the zone of theseal between the outer end of the main spark plug insulator and thecentral member of the terminal connection; a

a Fig. 3 is an expanded view of a portion of Fig. 1 about the terminalarea; and

4 is a section of Fig. 1 through the line 4+"-4.

Although a single embodiment of the present invention is illustrated inthe drawings in the form of a con nector for connecting a radio-shieldedconductor of high potential electrical energy to the input terminal of aradio-shielded spark plug in the ignitionsystemof an in ternalcombustion engine, it will be understood, how'- ever, that the inventionhas novel utility in many other electrical types of systems.

Fig. 1 shows a particular embodiment of the invention wherein spark plug1 is of the type comprising a metal shell 3 adapted to be threaded intothe cylinder ofan engine. Mounted in shell 3 in any suitable known man'-neris a' tubular insulator 5 which supports a center electi'ode 7 andinsulates it from the shell. The upper or Patented Nov. 17, 1959 'iceouter end of insulator 5 has an enlarged bore forming a recess 9 at theinner end of which is the terminal 11 of the'center electrode. The parts7, 11 herein called a center electrode and terminal may be an insulatedconductor of any other type of electrical device.

Projecting upwardly from said shell 3 is a metallic barrel or tube 16which serves as a radio-shielding element and is preferably at somedatum potential, normally ground. The upper extremity of the barrel 16is externally threaded for cooperation with a tubular, internallythreaded nut 18, thereby operatively connecting the barrel and conduit20 to etlect a continuous metallic enclosure for an electricalconductor. As illustrated, the conduit 20 comprises a flexible tube orconduit 22 having a rigid fitting or ferrule 24 soldered or otherwisesuitably secured to the end thereof. Nut 18 has an internal flange orshoulder 28 at its upper periphery which engages an external shoulder 30at the lower periphery of ferrule 24, so that the latter and barrel 16are held in firm end-to-end engagement when the nut is screwed home onthe barrel. This type of construction assures external continuitybetween the flexible conduit and the spark plug shell thus resulting inimproved radio-shielding.

Extending from conduit 22 downward into shell16 is an electric conductor32, having the usual electrical insulation 34, and terminating at itsfree end in a terminal 36 whose contact surface 38 is flat,non-comprwsible and void of any abutting compressible elements.

Fig. 3 shows an expanded view of the electrical conduc'tor termination36 and the structural elements which comprise the said termination. Thelower end of said conductor is stripped of a portion of its insulation34, baring a portion of the conductor 32 sufficient to slidably engagethe inner portion of a cylindrical metal bushing 37, preferably of brassand the like. The metal bushing 37 has its upper end portion 44 abuttingthe conductor insulation 34 and its lower end portion extending beyondthe free end of the said conductor thereby forming a frusto-conicalrecess 35 between the said bushing and conductor at their lowerextremities. A conductive pin, nail and the like 46 is driven in at thecentral portion of said conductor at its lower extremity to become anintegral part of said conductor, the head of said pin extending beyondthe end of said conductor, but completely shielded by the recess formedbetween said bushing 37 and conductor 32. The spread out lower end ofconductor 32 in recess 35, nail 46 and bushing 37 are integrally securedby filling the recess 35 with solder and the like, the base portion ofsaid recess thereby forming the contact terminal 36 of the upperconductor.

The metal bushing 37 intermediate its lower end portion has a recessedannular groove 50 in which is fitted a spring metal washer 52 whoseouter periphery extends sufiiciently outward to structurally support atubular insulator 58 at its lower extremity 60. The tubular insulator 58is preferably made from rigid ceramic material and the like and enclosessaid electrical conductor 32 in sleeve-like fashion in an axialdirection, extending up to the threaded portion of barrel 16.

Intermediate the tubular insulator 58 and said electrical conductorinsulation 34 isa flexible insulated sleeve. member 62, preferably madefrom Silastic tubing and the like, which normally has an inner diametersmaller than the outer diameter of conductor insulation 34 necessitatingpressure means forcibly applying said seleeve to said insulator insleeve-like fashion to effect a seal tight force fit. The sleeve 62extends from a point at its upper extremity slightly below the upperextremity of said tubular insulator 58 and terminates at its lowerextremity 35 ata point at which the lower end of the electrical con--ductor is stripped of its insulation to form the lower terminal 36. Thepresence of this type of sleeve minimizes the danger of flashovers orsparking between the inner conductor and the barrel l6.

Further novel sealing means are provided for preventing moisture and thelike from penetrating or leaking through the connector assembly therebyavoiding any low resistance leakage paths between the high voltage cableportions and the connector shell or ground, the said low resistanceleakage paths being highly conducive to flashover, arcing and the like.

One such means is providing a cylindrical rubber-like member 70 disposedaround and tightly engaging the conductor insulation 34 at the upperextremity of said flexble sleeve 62 and substantially abutting the endportion thereof. The cylindrical rubber-like member 73 has intermediateits end portions an extended shoulder or flange 72 Whose lower surface74 is beveled or inclined to slidably engage the upper beveled orinclined surface 76 of said tubular insulator 58, the said beveledsurfaces being complementary to each other. The upper portion or surface73 of said extended flange 72 is flat and has seated thereon an annularmetal washer 80.

In order to provide a firm engagement and tight seal at the engagingsurfaces of flange '72 and tubular insulator 58 novel simplified meansare comprehended by this in vention for applying a sufiiciently largeyielding pressure to the upper face of the flange '72 during the act ofconnecting the barrel and cable portions. Saidmeans in the form showncomprises a coil spring 82 interposed between said washer 80 andinternal flange 84 of ferrule 24 at its upper extremity. An additionalnovel and improved seal is provided by the use of an annular rubber-likemember 9% which surrounds the upper end portion of tubular insulator 58and is also seated upon the upper end portion of the tubular insulatorthereby effecting a spark-proof seal between conductor and ground whenthe conduits are operatively connected in end-to-end engagement.

The annular sealing member 9% has an inclined upper surface 92, saidsurface being adapted to engage under pressure resilient coil springmeans 94, the said coil spring means being interposed between saidinclined surface 92 and an internal shoulder 96 intermediate the endportions of said ferrule 24.

When the parts are in the assembled relation shown, the springs 82, fitare both under predetermined axial compression providing sealing ascontemplated by this invention. When the compressing forces are releasedby the unscrewing of the ferrule 2 the upper cable assembly iscompletely removable as a single integral unit, so that when the nut 18is screwed into barrel 16, the coil spring means 82, 94 will becompressed with a minimum of relative movement of the input conductorand its shielding conduit.

Although only a single embodiment of the invention is illustrated in theaccompanying drawings it is to be expressly understood that theinvention is not limited thereto. Various other changes may also be madein the design and arrangements of parts illustrated as well as in thematerials suggested without departing from the spirit and scope of theinvention as will now be understood by those skilled in the art.

What is claimed is:

1. In apparatus of the class described a tubular metallic barrelexternally threaded at one end thereof, an electrical insulator having arecess therein mounted in said barrel, a terminal at the inner end ofsaid recess, a flexible shielding conduit, a ferrule secured to the endof said conduit and extending beyond the conduit, the extending portionof said ferrule having an external shoulder, a nut threaded onto saidbarrel and having an internal shoulder engaging an external shoulder onsaid ferrule to hold the ferrule and barrel in end-to-end contact, aninsulated electrical conductor extending from said conduit into saidrecess, a conductor termination including a rigid terminal at the endthereof engaging the terminal in said recess, an insulating sleeveclosely surrounding the projecting end of said conductor, an annularinsulator supportable by said conductor termination and surrounding saidsleeve, a first sealing member extending upward beyond said sleeve andsurrounding said conductor, said sealing member having an externalshoulder engageable with said annular insulator at its upper endportion, a second sealing member surrounding said annular insulator atits upper periphery and mounted on said barrel insulator at its upperend portion, an inner coil spring interposed between an internal uppershoulder of said ferrule and the shoulder of said first sealing member,and an outer coil spring interposed between an internal shoulderintermediate the end portion of said ferrule and the said second sealingmember, said inner and outer springs being maintained under axialcompression when the apparatus is assembled to press the said firstsealing member into sealing engagement with the upper end of said sleeveand annular insulator and the second sealing member into sealingengagement with the upper extremity of said in sulator and annularinsulator.

2. Apparatus as defined in claim 1 wherein said conductor terminationcomprises an annular metal washer integral therewith and whose outerperiphery extends outwardly sufiicient to structurally support saidannular insulator.

3. In apparatus of the class described, a radio-shielding conduitassembly comprising a tubular metallic conduit shell, the conduit shellcomprising two metallic conduit sections releasably held in end-to-endengagement, a first, outer insulating tube aflixed in a first section ofsaid shell, a first contact extending transversely of the first tube,and fixedly mounted on the first tube, a second, elon gated, rigid innerinsulating tube slidably mounted within the first insulating tube in theshell, an electrical conduc-' tor extending into the shell and thesecond tube, a second contact connected to the conductor, rigidlyaffixed to the inner end of the second tube, and engaging the firstcontact, a first annular compressible sealing means interposed betweenthe conductor and the outer end of the second, inner tube, a coilcompression spring extending axially of the tubes and having the innerend thereof engaging the annular sealing means and the outer end thereofcompressibly acting upon the second section of the shell, whereby thecontacts are constantly maintained in forcible engagement with eachother, a second annular compressible sealing member interposed betweenthe outer end of the first, outer tube and the conduit shell, and asecond, larger diametered, coil compression spring acting between thesecond section of the conduit shell and the second annular sealingmeans.

4. Apparatus as defined in claim 3, wherein the second annular sealingmeans overlies and sealingly engages the outer end of the first, outertube.

5. In apparatus of the class described a tubular metallic barrel, anelectrical insulator having a recess therein mounted in said barrel, aterminal at the inner end of said recess, a flexible conduit, a ferrulesecured to the end of said conduit and extending beyond the conduit,means to hold the ferrule and barrel in end-to-end contact, an insulatedelectrical termination including a rigid terminal at the end thereofengaging the terminal in said recess, an insulating sleeve closelysurrounding the end of said conductor projecting into said recess, anannular insulator supported by said conductor termination andsurrounding said sleeve, a first sealing member extending up ward beyondsaid sleeve and surrounding said conductor, said sealing member havingan external shoulder engageable with said annular insulator at its upperend portion, a second sealing member surrounding said annular insulatorat its upper periphery and mounted on said barrel insulator at its upperend portion, an inner coil spring inter- 2,913,696 5 6 posed between aninternal upper shoulder of said ferrule References Cited in the file ofthis patent and the shoulder of said first sealing member, and an outercoil spring interposed between an internal shoulder UNITED STATESPATENTS intermediate the end port-ion of said ferrule and the said1,896,444 Fossati Feb. 7, 1933 second sealing member, said inner andouter springs being 5 2,318,822 Wantz May 11, 1943 maintained underaxial compression when the apparatus 2,409,732 Browne et al. Oct. 22,1946 is assembled to press the said first sealing member into 2,442,858Nims et a1. June 8, 1948 sealing engagement with the upper end of saidsleeve and 2,684,398 Strunk July 20, 1954 annular insulator and thesecond sealing member into 2,694,187 Nash Nov. 9, 1954 sealingengagement with the upper extremity of said insu- 10 2,759,040 KnudsonAug. 14, 1956 lator and annular insulator. 2,759,989 Anderson Aug. 21,1956

